Methods of finishing quartz glass surfaces and components made by the methods

ABSTRACT

Methods of surface finishing a component useful for a plasma processing apparatus are provided. The component includes at least one plasma-exposed quartz glass surface. The method includes mechanically polishing, chemically etching and cleaning the plasma-exposed surface to achieve a desired surface morphology. Quartz glass sealing surfaces of the component also can be finished by the methods. Plasma-exposed surface and sealing surfaces of the same component can be finished to different surface morphologies from each other.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 10/448,422 entitled METHODS OF FINISHING QUARTZ GLASS SURFACES ANDCOMPONENTS MADE BY THE METHODS, filed on May 30, 2003, the entirecontent of which is hereby incorporated by reference.

BACKGROUND

Plasma processing apparatuses are used to perform processes includingplasma etching of substrates made of semiconducting, dielectric andmetallic materials, physical vapor deposition, chemical vapor deposition(CVD), ion implantation and resist removal.

Plasma processing apparatuses include components that are exposed toplasma environments. In view of the desire to increase process yields,there is a need for plasma-exposed components that provide for reducedparticle contamination in such plasma environments.

SUMMARY

Methods for finishing quartz glass surfaces are provided. The methodscan produce quartz glass surface finishes that reduce the incidence ofquartz and metal particulate, and molecular metal contamination whenused in plasma processing apparatuses. Components having such finishedquartz glass surfaces are also provided.

A preferred embodiment of a method of surface finishing a componentincluding at least one quartz glass surface comprises mechanicallypolishing at least one quartz glass surface of the component, chemicallyetching the mechanically polished quartz glass surface, and cleaning theetched quartz glass surface to remove metal contaminants from thesurface.

Components finished by preferred embodiments of the methods include atleast one plasma-exposed quartz glass surface. The components can alsoinclude at least one non-plasma-exposed quartz glass surface, such as avacuum sealing surface. Plasma-exposed surfaces of the components can befinished to a different surface morphology than non-plasma-exposedsurfaces. The finished components can be used in plasma processingapparatuses to provide for reduced contamination of substrates.

Methods of surface finishing components preferably achieve low levels ofmetal contaminants on quartz glass surfaces. The components preferablycan provide for reduced metal particulate and molecular metalcontamination of substrates when used in plasma processing apparatuses.

Preferred embodiments of the methods can be used to finish componentsthat have either been previously exposed, or have not been previouslyexposed, to plasma in the plasma processing apparatus.

Preferred embodiments of methods of etching semiconductor substrates ina plasma chamber of a plasma processing apparatus, which contains one ormore components that have been finished as described above, are alsoprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an SEM micrograph (at 1000×) of a slurry-polished quartz glasssurface.

FIG. 2 is an SEM micrograph (at 1000×) of a quartz glass surface thathas been slurry-polished and plasma conditioned.

FIG. 3 shows a flow chart of a first preferred embodiment of a quartzglass finishing process.

FIG. 4 is an SEM micrograph (at 1000×) of a quartz glass surface treatedaccording to a preferred embodiment of the quartz glass finishingprocess.

FIG. 5 shows the relationship between the number of particles added to asilicon wafer during a plasma etch process, for a quartz glass windowprocessed according to a preferred embodiment (“□”), and for aslurry-polished quartz glass window (“♦”).

FIG. 6 shows the number of atoms/cm² of different metals on aslurry-polished quartz glass component without exposure to plasma (“A”),a slurry-polished quartz glass component that has been exposed to plasma(“B”), and a quartz glass component processed according to a preferredembodiment (“C”).

FIG. 7 shows a flow chart of a second preferred embodiment of a quartzglass finishing process.

FIG. 8 shows a slurry-ground sealing surface of a quartz glasscomponent.

FIG. 9 shows a dielectric window including plasma-exposed and sealingsurfaces that can be treated by the quartz glass finishing method.

FIG. 10 is an enlarged partial view of the dielectric window shown inFIG. 9.

FIG. 11 shows a gas injector including plasma-exposed and sealingsurfaces that can be treated by the quartz glass finishing method.

DETAILED DESCRIPTION

Particle performance is a concern in the processing of variousmaterials, such as semiconductor materials, dielectric materials andmetals, in plasma processing apparatuses. Particulate contaminants thatadhere to substrates processed in plasma reactors can reduce productyield. One source of particulate contamination in plasma reactors is aplasma exposed surface of a component.

Components including plasma-exposed surfaces can be made by processesincluding sintering and/or machining of one or more surfaces of thecomponents. These steps result in damage to the surfaces, leaving thesurfaces fractured and discontinuous. These fractures are a potentialsource of particle generation during plasma processing. Slurry polishingcan reduce the size of the particles; however, it does not eliminate theparticles. FIG. 1 is a scanning electron microscope (SEM) micrograph ofa surface of a quartz glass dielectric window that has beenslurry-polished. Quartz glass surfaces that have been machined by othertechniques have damage similar to that shown in FIG. 1.

It has also been determined that components made of quartz glass can beinstalled in a plasma reactor and conditioned before achievingproduction conditions for semiconductor substrates in the plasmareactor, in order to reduce the incidence of quartz-related particulatecontamination of the substrates. Conditioning wafers may be installed inthe plasma reactor during conditioning. The plasma removes material fromthe plasma-exposed surfaces of the components by etching. Plasma-exposedsurfaces preferably have a morphology that reduces quartz and metalparticulate. Eventually, enough quartz material is removed by theconditioning treatment to achieve an acceptable surface quartzparticulate level. FIG. 2 is an SEM micrograph of a surface of a quartzglass dielectric window that has been slurry-polished and thenconditioned in a plasma reactor by plasma exposure (50 hours).

However, conditioning treatments require many hours of lost productiontime, and can require up to ten or more days, to produce a suitablesurface finish on plasma-exposed surfaces of components for use inplasma processing. Accordingly, such conditioning treatment requiressignificant down time of the plasma reactor in order to achieve suitableparticle performance by the components. In addition, the conditioningtreatment requires associated expenses, including the costs ofconditioning wafers, operator monitoring, and intervention.

In addition, surfaces of quartz glass components that need to provide avacuum seal in plasma reactors to prevent air flow paths in a plasmaprocessing chamber, i.e., sealing surfaces (for example, O-ring sealingsurfaces), need to have a finish that provides suitable vacuum sealingperformance. Such sealing surfaces are not plasma-exposed surfaces.However, a desirable vacuum seal surface finish can be significantlydifferent from a desirable plasma-exposed surface. It has beendetermined that components having both plasma-exposed and vacuum sealsurfaces preferably should have significantly different surface finishesat these different locations on the same component.

FIG. 3 shows a flow chart of a first preferred embodiment of a method ofsurface finishing quartz glass. The method can be practiced to finishone or more quartz glass surfaces of a component useful for a plasmaprocessing apparatus. The one or more finished surfaces preferablyinclude at least one surface that is exposed to plasma when thecomponent is installed in a plasma reactor. The component can be a gasinjector, dielectric window, electrode, view port, edge ring, focusring, confinement ring, or the like, for a plasma reactor.

Preferred embodiments of the methods of finishing quartz glass can beused to finish quartz glass surfaces of components made of quartz glass,as well as quartz glass surfaces (for example, coatings) of componentsthat may comprise materials other than quartz glass.

The method preferably includes mechanical polishing, chemical etching,and cleaning steps to produce a desired surface finish on a component.Components that can be processed by the method can have various shapes,such as plate shapes, disk shapes, ring shapes (for example, dielectricwindows, view ports, edge rings, and the like), and cylindrical shapes,and surfaces having combinations of different shapes. The components canhave various sizes.

The quartz glass components are preferably made of flame-fused naturalquartz. Flame-fused natural quartz is typically available in the form ofboules, which can be processed to the desired shape and size. The quartzglass can alternatively be arc-fused natural quartz, or syntheticquartz, for example.

Prior to performing the finishing treatment, the quartz glass materialpreferably has a bulk purity level of any metal of less than about 10ppm. This metal purity level in quartz glass can provide a metal levelresulting from the bulk that is much lower than the surface metal level.Reducing the impurity level of metals in the quartz glass materialreduces the incidence of particles and/or on-substrate defects relatedto the metals.

Quartz glass components that may be finished by preferred embodiments ofthe method can be in a machined and/or sintered condition. For example,plate-shaped quartz glass components can be cut from a boule andmachined to a desired shape. Machined and/or sintered components can bemachined to a desired configuration and surface condition using anysuitable process, such as diamond grinding, or the like.

The quartz glass components are preferably mechanically polished to adesired surface finish. The mechanical polishing preferably involvesslurry-polishing one or more surfaces of the component to a desiredsurface finish. The slurry can contain a suitable abrasive materialincluding, for example, aluminum oxide, silicon carbide, diamond, ceriumoxide, zirconium oxide, or the like. The abrasive material preferablyhas a particle size that produces a desired surface finish level on theslurry-polished surface(s) of the component.

The mechanical polishing of the quartz glass component preferably canachieve the same surface finish, or alternatively can achieve adifferent surface finish, at different surface locations of thecomponent. For example, one or more plasma-exposed surfaces of thecomponent can be mechanically polished to a different surface finishthan one or more non-plasma-exposed surfaces (for example, sealingsurfaces).

The mechanical polishing preferably achieves a desired quartz glasssurface morphology prior to chemical etching so that the etchingachieves a surface morphology similar to a plasma-exposed surface. Forexample, the etched surface preferably has the same effective surfacearea, and is essentially damage-free and fracture-free. The mechanicallypolished surface morphology can be quantified, for example, by thearithmetical mean roughness, R_(a). In a preferred embodiment, the R_(a)of the mechanically polished surface(s) is preferably about 5-30microinches (about 0.125-0.75 microns), and more preferably about 12-20microinches (about 0.3-0.5 microns). For a given component, differentsurfaces can be mechanically polished to different finishes. Forexample, plasma-exposed surfaces can be mechanically polished to a lowerR_(a) value (i.e., a smoother finish), than non-plasma-exposed surfaces,for which particulate removal during plasma processing is of lessconcern.

The machining and mechanical polishing steps can result in fracturedsurfaces, which are a source of particles of quartz glass and/or metalon machined and/or mechanically polished surfaces of the component. Theattached particles can be a source of particle contamination duringplasma processing of substrates. Accordingly, it is desirable to reducethe number of attached particles to a suitably low count prior to theprocessing of substrates with the component present in the plasmareactor. As described above, attached particles can be removed fromplasma reactor components by plasma conditioning techniques; however,these techniques are not completely satisfactory.

Accordingly, the etch step preferably removes attached quartz glass andmetal contaminant particles from the treated component surface(s), andpreferably achieves a surface morphology that is similar to that of aplasma-exposed surface. The etch step preferably uses afluorine-containing etching liquid that is effective to etch quartzglass. For example, the fluorine-containing etching liquid can be anetching solution containing hydrofluoric acid (HF), ammonium fluoride(NH₃HF), ammonium bifluoride (NH₄FHF), or mixtures thereof. The etchingliquid also can contain additives, such as nitric acid (HNO₃), or otheracids. The concentration, temperature, and pH of the etching liquid, theetching time, and other parameters of the etching liquid and etchingprocess, can be selected to achieve the desired rate and depth ofremoval of surface material from the component.

The surface morphology of the etched surface can be characterized, forexample, by the R_(a) value of the surface. The etch step preferablyachieves an R_(a) value of about 1-100 microinches (about 0.025-2.5microns) at one or more selected surfaces of the component. As explainedbelow, the R_(a) value that is desired for a given component surface canvary depending on the type of component, as well as the type of surfacefinished (for example, plasma-exposed surfaces versus non-plasma-exposedsurfaces).

By changing the surface morphology of the component by etching, theactual surface area of the component is changed. The nominal surfacearea of the component is determined by its physical dimensions. Theactual surface area of the component additionally takes into accountsurface roughness. Increasing the surface roughness increases the actualsurface area of a component. The chemical etching step preferablyachieves a ratio of the actual surface area/nominal surface area of thecomponent that approximates the ratio that plasma-exposed (or plasmaconditioned) components can have. The chemical etching step preferablyachieves a ratio of the actual surface area/nominal surface area of thecomponent of about 1.1-4, and more preferably about 1.2-1.5.

The surface morphology of the component resulting from the etching stepcan also be characterized by the feature length of the surfacemorphology, which provides a measure of the spatial frequency of thesurface roughness. The feature length of the etched surface of thecomponent preferably is about 1-50 microns. The desired feature lengthvalue for a given surface can depend on the type of component that isfinished, as well as the type of surface (for example, plasma-exposedsurfaces versus non-plasma-exposed surfaces).

The cleaning step removes metal contaminants from the surface of theetched quartz glass component. The cleaning step comprises contactingthe quartz glass component with a liquid having a suitably highsolubility for metals that, if present, preferably are removed from thecomponent by the cleaning. Such metals include, but are not limited to,Al, B, Ca, Cr, Cu, Fe, Li, Mg, Ni, K, Na, Ti and/or Zn. Suitablesolvents that can be used for cleaning quartz glass to remove thesemetals include, but are not limited to, nitric acid (HNO₃), hydrofluoricacid (HF), phosphoric acid (H₃PO₄), oxalic acid (COOH)₂, formic acid(HCOOH), hydrogen peroxide (H₂O₂), hydrochloric acid (HCl), acetic acid(CH₃COOH), citric acid (C₆H₈O₇), and mixtures thereof.

In addition, to achieve the desired cleanliness level of the quartzglass parts, careful part handling, use of ultrapure solvents (forexample, solvents containing less than about 10 ppb metal impurities),and environmental control, such as the use of a Class 100 cleanroom fordrying and packaging, are preferred.

The cleaning step reduces the surface metal contamination level of thequartz glass component for one or more of Al, B, Ca, Cr, Cu, Fe, Li, Mg,Ni, K, Na, Ti and Zn to a desirably low level, which is preferably lessthan about 1,000×10¹⁰ atoms/cm², more preferably less than about100×10¹⁰ atoms/cm², and most preferably less than about 10×10¹⁰atoms/cm².

FIG. 4 is an SEM micrograph of a surface of a quartz glass dielectricwindow that has been treated by mechanical polishing, etching andcleaning steps according to a preferred embodiment.

FIG. 5 shows test results demonstrating the level of particlecontamination (number of particles sized larger than 0.16 μm added to asilicon wafer during a plasma etching process) for a quartz glass windowprocessed according to a preferred embodiment (“□”) compared to aslurry-polished quartz glass window (“♦”). In the curves, zero RF hourscorresponds to the installation of the window in the plasma reactor. Thecurves show that the number of particles added by the quartz glasswindow finished by the preferred embodiment was much lower than thenumber of particles added by the slurry-polished quartz glass windowover the entire test period. Most of the particles that were added bythe slurry-polished quartz glass window during about the first two RFhours were quartz particles. Although the number of particles added bythe slurry-polished quartz glass window was decreased by the plasmaexposure, the number of these particles did not reach the lower numberof particles added by the quartz glass window finished by the preferredembodiment during the test period.

Accordingly, the test results shown in FIG. 5 demonstrate that thefinishing treatment can produce components for plasma processingapparatuses having finished surfaces characterized by much lower numbersof added particles when used in plasma environments, as compared toslurry-polished quartz glass windows. In addition, the test results showthat only a short RF treatment (for example, about ½ hour) may bedesirable for components treated according to preferred embodiments ofthe method in order to achieve a steady state particle level (forexample, about 10 particles larger than 0.16 μm added). Accordingly,apparatus downtime and expenses associated with plasma conditioning canbe significantly reduced by using components finished by preferredembodiments of the method.

FIG. 6 shows the test results for the number of atoms/cm² of Al, B, Ca,Cr, Cu, Fe, Li, Mg, Ni, K, Na, Ti, and Zn present on a slurry-polishedquartz glass component without exposure to plasma (“A”), aslurry-polished quartz glass component subjected to plasma exposure(“B”), and a quartz glass component processed according the preferredembodiment (“C”), respectively. As compared to the slurry-polishedquartz glass component, and the slurry-polished and plasma-exposedquartz glass component, the finishing treatment according to thepreferred embodiment significantly reduced the surface metalcontamination level for each of the metals. Metal contamination isundesirable because it can create defects in integrated circuitsprocessed in a plasma reactor chamber containing contaminated quartzglass, either as particles deposited onto wafer surfaces, or asmolecular contamination that diffuses into wafers and introducesundesirable impurities that adversely affect doping profiles, as well aswafer properties. Accordingly, preferred embodiments of the methods oftreating quartz glass can reduce this problem.

According to a preferred embodiment, the finishing treatment can beperformed to recondition parts that have previously been exposed toplasma in a plasma reactor chamber (i.e., “used parts”) to achievesurface metal levels that are comparable to the levels that can beachieved by the finishing treatment for new parts, i.e., parts that havebeen treated by the finishing treatment, but have not been used in aplasma reactor chamber during plasma processing. In such embodiments,the parts are preferably only subjected to the cleaning step.

FIG. 7 shows the steps of a second preferred embodiment of a method ofsurface finishing quartz glass. The method can be performed to finishone or more plasma-exposed quartz glass surfaces, and one or more quartzglass vacuum sealing surfaces, of a quartz glass component for a plasmareactor. Components that may have plasma-exposed surfaces and vacuumsealing surfaces include, gas injectors, view ports, and dielectricwindows for plasma reactors, for example.

As shown in FIG. 7, the second preferred embodiment includesmechanically polishing one or more surfaces of the quartz glasscomponent, as in the first preferred embodiment described above.

In the second preferred embodiment, one or more quartz glass sealingsurface are finished to a desired finish. FIG. 8 shows an exemplaryfinish of a surface that can be formed on a quartz glass component bymechanical polishing (e.g., slurry grinding). The mechanical polishingprocess produces a sealing surface having a concentric circular patternof grooves. The concentric grooves reduce, and preferably prevent, thepassage of air to maintain desired vacuum integrity at the sealingsurface.

According to the second preferred embodiment, one or more mechanicallypolished sealing surfaces of the quartz glass component are masked priorto the etching step to prevent the sealing surface(s) from also beingetched. Accordingly, the etching step is performed to etch surfaces ofthe component other than the sealing surface(s). The sealing surface(s)of the quartz glass component can be masked using any suitable maskingmaterial, such as a contaminant-free tape and/or wax.

In the second preferred embodiment, after the etch step, the mask isremoved from the sealing surface(s) and the component is cleaned, asdescribed above for the first preferred embodiment. The cleaning stepremoves metal contaminants from surfaces of the etched quartz glasscomponent, including both sealing surfaces and non-sealing surfaces(i.e., plasma-exposed surfaces).

FIGS. 9 and 10 show an exemplary dielectric window 20 including parallelplanar surfaces 22, a side surface 24, and a through passage 26. FIG. 10is an enlarged view of the passage 26, showing a vacuum sealing surface28 and plasma-exposed planar surfaces 22. The vacuum sealing surface 28can be an O-ring sealing surface, for example. The dielectric window 20can have more than one sealing surface. Dielectric windows made ofquartz glass, such as the dielectric window 20, can be finished by thefollowing preferred procedure.

Plasma-exposed planar surfaces of the dielectric window 20 (for example,planar surfaces 22) are machined and mechanically polished. Themechanically polished, plasma-exposed surfaces preferably have a R_(a)value of about 5-20 microinches (0.125-0.5 microns), more preferablyabout 12-20 microinches (0.3-0.5 microns). The sealing surface 28 ismasked.

The plasma-exposed surfaces are wet etched using a fluorine-containingetching liquid to achieve a desired surface morphology. For example, anHF etching solution can be used to achieve an R_(a) value of about20-100 microinches (about 0.5-2.5 microns), more preferably 30-50microinches (about 0.75-1.25), for plasma-exposed surfaces. The etchedplasma-exposed surfaces have a preferred ratio of the actual surfacearea to the nominal surface area of about 1.1-4, more preferably about1.2-1.5. The characteristic feature length of the surface morphology ofthe plasma-exposed surfaces is preferably about 2-30 microns, morepreferably about 5-20 microns. For example, the average feature lengthcan be about 10 microns for the plasma-exposed surfaces.

The sealing surface 28, which is not etched, is polished to a preferredR_(a) value of about 10-20 microinches (0.25-0.5 microns). The surfacearea of the sealing surface is not of concern because it is not aplasma-exposed surface. The characteristic feature length of the sealingsurface is preferably about 5-25 microns.

The masking is removed from the sealing surface 28 and the dielectricwindow 20 is cleaned to remove metal contaminants from theplasma-exposed surfaces and other surfaces. The cleaning step reducesthe metal level of the cleaned surfaces of the dielectric window for oneor more of Al, B, Ca, Cr, Cu, Fe, Li, Mg, Ni, K, Na, Ti, and Znpreferably to less than about 1,000×10¹⁰ atoms/cm², more preferably lessthan about 100×10¹⁰ atoms/cm², and most preferably less than about10×10¹⁰ atoms/cm².

As another example, FIG. 11 shows a gas injector 40 including vacuumsealing surfaces 42, 44, and a plasma-exposed surface 46. The gasinjector 40 also includes inner plasma-exposed surfaces, such as aninner bore (not shown). The vacuum sealing surfaces 42, 44 can be O-ringsealing surfaces, for example. The gas injector can include othersealing surfaces (not shown). Gas injectors made of quartz glass, suchas the gas injector 40, can be finished by the following preferredprocedure.

The plasma-exposed surface 46 is machined and subjected to mechanicalpolishing to achieve an R_(a) value of about 7-20 microinches (0.025-0.5microns), more preferably about 7-12 microinches (0.075-0.3 microns).The plasma exposed surface 46 of the gas injector 40 is sufficientlysmall so that it does not significantly affect plasma chemistry.Accordingly, the plasma-exposed surface 46 preferably is as smooth aspossible after machining to allow the removal of damaged surfacematerial at desirably low HF concentrations and etching times during theetching step.

The plasma-exposed surface 46 can be etched using a fluorine-containingetching liquid, such as an HF etch solution, to achieve a desiredsurface finish. For example, the surface can have an R_(a) value ofabout 1-100 microinches (about 0.025-2.5 microns), more preferably 40-60microinches (about 1-1.5 microns). The gas injector outer surface is assmooth as possible after etching. The HF concentration and etching timecan be varied to achieve a desired plasma-exposed surface smoothness.

The sealing surfaces 42, 44 are polished to an R_(a) value preferably ofabout 12-20 microinches (0.3-0.5 microns). The characteristic featurelength of the sealing surfaces 42, 44 is preferably about 5-25 microns.

The masking is removed from the sealing surfaces 42, 44 and the gasinjector 40 is cleaned to remove metal contaminants from the outersurface. The cleaning step reduces the surface metal contamination levelof the gas injector 40 for one or more of Al, B, Ca, Cr, Cu, Fe, Li, Mg,Ni, K, Na, Ti, and Zn preferably to less than about 1,000×10¹⁰atoms/cm², more preferably less than about 100×10¹⁰ atoms/cm², and mostpreferably less than about 10×10¹⁰ atoms/cm².

Accordingly, preferred embodiments of the methods of finishing quartzglass can be used to finish components for plasma processing apparatuseshaving various sizes and shapes, and to provide different surfacefinishes at different surfaces of the components. Preferred embodimentsof the methods can provide plasma-exposed surfaces having improvedparticle performance for plasma reactors, as well as sealing surfaceshaving high vacuum integrity, on the same components.

While the invention has been described in detail with reference tospecific embodiments thereof, it will be apparent to those skilled inthe art that various changes and modifications can be made, andequivalents employed, without departing from the scope of the appendedclaims.

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 21. A component for a plasma processing apparatus,comprising: at least one plasma-exposed quartz glass surface having afirst arithmetical surface roughness R_(a); and at least one vacuumsealing quartz glass surface having a second arithmetical surfaceroughness R_(a) different from the first arithmetical surface roughnessR_(a).
 22. The component of claim 21, wherein the plasma-exposed quartzglass surface and the vacuum sealing quartz surface are of a materialselected from the group consisting of flame-fused natural quartz,arc-fused natural quartz, and synthetic quartz.
 23. The component ofclaim 21, wherein the plasma-exposed quartz glass surface has (i) anarithmetical mean roughness R_(a) of about 1-100 microinches, and (ii) aratio of actual surface area/nominal surface area of about 1.1-4 orabout 1.2-1.5.
 24. The component of claim 21, wherein the plasma-exposedquartz glass surface has a level of at least one metal selected from thegroup consisting of Al, B, Ca, Cr, Cu, Fe, Li, Mg, Ni, K, Na, Ti and Znof less than about 1,000×10¹⁰ atoms/cm², or less than about 100×10¹⁰atoms/cm², or less than about 10×10¹⁰ atoms/cm².
 25. The component ofclaim 21, wherein: the component is a dielectric window; theplasma-exposed quartz glass surface has at least one of (i) anarithmetical mean roughness R_(a) of about 5-20 microinches, or about12-20 microinches, (ii) a ratio of actual surface area/nominal surfacearea of about 1.1-4, or about 1.2-1.5, and (iii) a characteristicfeature length of about 2-30 microns, or about 5-20 microns; and thevacuum sealing quartz glass surface has at least one of (i) anarithmetical mean roughness R_(a) of about 10-20 microinches and (ii) acharacteristic feature length of about 5-25.
 26. The component of claim21, wherein: the component is a gas injector; the plasma-exposed quartzglass surface has an arithmetical mean roughness R_(a) of about 1-100microinches, or about 40-60 microinches; and the vacuum sealing quartzglass surface has an arithmetical mean roughness R_(a) of about 12-20microinches.
 27. A method of etching a semiconductor substrate in aplasma processing apparatus, comprising: installing a componentaccording to claim 21 in a plasma chamber of a plasma processingapparatus; and plasma etching at least one semiconductor substrate inthe plasma chamber.
 28. The method of claim 27, further comprisingplasma conditioning the component for less than about one-half hourbefore plasma etching the semiconductor substrate.